1. Field of the Invention
This invention relates to an aqueous absorption fluid composition, process and apparatus providing improved water vapor absorption and thermal transfer. Addition of small quantities of certain ethers to an aqueous absorption fluid composition provides improved heat and mass transfer resulting in improved water vapor absorption and enhanced thermal and chemical stability. The compositions of this invention are particularly suited for use in high temperature stages of thermal transfer loops used in absorption refrigeration, chilling, heat pump, energy storage and other thermal transferring applications.
2. Description of Related Art
Aqueous metal halide solutions are well known as refrigerant/absorbent solutions for absorption refrigeration systems as taught by U.S. Pat. No. 3,478,530.
Alcohols have been widely used as additives in small amounts to aqueous refrigerant absorbent solutions for improved heat transfer. Octyl alcohol in LiBr solutions is taught by U.S. Pat. No. 3,276,217 and 4,857,222; certain secondary alcohols in LiBr solutions are taught by U.S. Pat. Nos. 3,609,087 and 4,315,411; certain tertiary alcohols are taught by U.S. Pat. No. 3,580,759; and fluoroalcohols are taught by U.S. Pat. No. 3,783,631.
Amines have been used as additives in small amounts to aqueous absorption systems for increased rate of water vapor sorption of working fluid as taught by U.S. Pat. Nos. 5,419,145; 5,577,388 and 5,829,259, for example.
Certain ethers are known as solvents for refrigerant methyl chloride used in absorption refrigeration as taught by U.S. Pat. No. 2,040,905.
Ethylene glycol monobutyl ether and diethylene glycol monobutyl ether additives, in amounts of 0.001 to 1.0 percent by weight, in concentrated lithium halide aqueous solutions are known as vapor pressure depressants for use in absorption refrigeration systems, as taught by U.S. Pat. No. 3,553,136.
The use of ether, specifically tetraethylene glycol dimethylether, as an absorbent in conjunction with an azeotropic mixture of trifluoroethanol and water as a cooling medium is taught by Japanese Patent Number 61-14282 to afford a wider temperature range of a cycle than a water/LiBr system in absorption refrigeration.
An absorption fluid of aqueous solutions of metal salts of alkali metal hydroxides, nitrites, and alkaline earth and transition metal hydroxides, halides and thiocyanates and about 10 to about 30 weight percent, based on the metal salt, of an organic compound including ethers, particularly alkaline glycol ethers is taught by U.S. Pat. No. 5,529,709 to provide increased absorbent solubility and vapor pressure reduction.